Hitherto, there has been proposed an arrangement for transporting non-driven trucks on a predetermined track, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-209309.
This prior art arrangement includes a predetermined track on which movable members are free to move, a movable-member transport device disposed in an upstream portion of the predetermined track, a brake device disposed in a downstream portion of the track, and another movable-member transport device disposed downstream of the brake device for transport to a next stage. Each movable-member transport device consists of a pair of feed rollers, right and left, abuttable to sides of each movable member, and a rotary drive device for imparting a forward rotational force to the feed rollers. The brake device consists of a pair of brake rollers, right and left, abuttable to sides of each movable member, and a torque motor for imparting a reverse rotational force to the brake rollers. The forward rotational force is set greater than the reverse rotational force.
According to such prior art arrangement, the feed rollers which are in abutment with the sides of the movable member are forcibly rotated by the rotary drive device to apply large propulsive force to the movable member, whereby the movable member which carries thereon an object to be transported can be transported on the predetermined track. In this case, the movable member goes into abutment against an immediately preceding movable member which is at a halt, so that a series of movable members including that immediately preceding one is pushed forward for being transported.
At a downstream location on the predetermined track, the brake rollers which are in reverse rotation are in abutment with the sides of a movable member and accordingly a reverse propulsive force acts upon this movable member. Since the forward rotational force is greater than the reverse rotational force, the brake rollers are rotated forward while being subjected to a braking force corresponging to the difference between the forward and reverse rotational forces. Thus, movable members on the downstream side are transported with a braking force applied thereto, so that the series of movable members is transported while being sequentially pushed from behind in closedly connected condition, without any gap created between adjacent movable members.
In the course of such transportation, various operations, such as part fitting and assembling, are carried out with respect to the object being transported. Each movable member as pushed forward by the brake device is similarly transported by the next movable-member transport device to the next stage of operation.
According to this prior art arrangement, movable members are sequentially transported forward by a plurality of movable-member transport devices on the predetermined track which is held in horizontal condition. Therefore, the speed of movable member transport is generally constant and accordingly various operations required with respect to objects being transported can be conveniently carried out. However, transport at constant speed means inefficient transport, for example, in a track portion in which no particular operation is carried out. Further, the fact that movable members are transported in closely spaced relation over almost the entire length of the predetermined track necessitates a large number of costly movable members, resulting in high cost of equipment. Especially where the predetermined track is exceptionally long, an excessively large number of movable members is required, which results in further increase in the cost of equipment. In addition, the fact that the predetermined track, inclusive of the non-operating track portion, is loop-shaped in plan view means that the planar space occupied by the entire arrangement is considerably large, which is very inconvenient from the standpoint of space economy.